Lettering pen



FIG. 1 is a left side elevational view of a lettering pen showing my new design;

FIG. 2 is a fragmentary front elevational view of the upper portion of the lettering pen;

FIG. 3 is a fragmentary elevational view thereof with the cap removed;

FIG. 4 is a bottom plan view thereof;

FIG. 5 is a top plan view thereof. 

The ornamental design for a lettering pen, substantially as shown and described. 